1. Field of the Invention
The present invention concerns a refrigeration apparatus using plural air cooled condensers, and in particular concerns a condenser design and arrangement of the components of a refrigeration circuit, to result in improved condenser heat transfer, efficient space utilization and noise reduction.
2. Description of the Related Art
The condenser which is used in a refrigerating unit is typically constructed of a single unitary body, having a general rectangular parallelepiped shape, the condenser being made up of piping, through which a refrigerant flows after exiting from a compressor, and heat exchange plates (or fins). A fan is provided for blowing air onto the heat exchange plates as the refrigerant passes through the pipe. As a result, when the refrigerant enters into the condenser from the compressor, it is in a gaseous state and gradually condenses to a liquid state inside the piping of the condenser.
However, when the refrigerant is converted into a liquid state, the volume of the refrigerant decreases dramatically inside the condenser piping. Assuming the internal diameter of the condenser piping remains the same, then due to the decrease in volume, the flow velocity of the refrigerant thus also drops dramatically when the refrigerant changes into a condensed liquid. Moreover, the flow velocity of the refrigerant is a fundamental parameter in determining the heat transfer coefficient of the refrigerant flowing inside the pipe, as well as the overall heat transfer efficiency of the condenser itself.
Various condenser manufacturers have provided designs in which two or three pipes are used at the inlet of an air cooled condenser, wherein midway through the condenser, the pipes are merged together into a single pipe. In this way, the total effective diameter of the condenser piping decreases to compensate for the decrease in volume of the refrigerant in the liquid phase. However, the condenser itself is still a single unit. Because of this, the size of the overall body of the refrigerating unit is basically determined by the size of the air cooled condenser itself, which is the largest single component of the refrigerating unit. Furthermore, when such a large single-body condenser is used, by necessity the fan therefor is also large, with the disadvantage that noise and vibration produced by the refrigerating unit are also quite large.
A condenser design like that described above is disclosed in U.S. Pat. No. 4,831,844 to Kadel. More specifically, in Kadle, a first fin and tube type condenser segment is defined by a dual flow arrangement by connecting an inlet port to a Y-type connector. The incoming refrigerant gas thus flows in parallel pairs of front and back rows of plural tubes. After such a parallel flow, another Y-type connector is used to combine the flows from the plural tubes into a single tube which continues to the outlet of the condenser. However, as indicated above, although two condensing stages are provided, the condenser of Kadle is essentially a single unit, and the condensing stages are not separated into respective condenser units, each having its own fan, in such a way to permit other components of the refrigerating unit (such as the compressor, evaporator, etc.) to be located between respective condenser units.
There have also been arrangements in which two or more condensers are arranged in series, or wherein multiple fans are provided for a single condenser unit, but such arrangements have not provided any improvement in heat transfer efficiency, especially in the liquid phase part of the condenser. Furthermore, these arrangements still provide the condenser section only on one side of the air conditioning unit. Since the condenser size overall is very large, such designs do not make efficient use of the space inside the housing of the refrigerating unit, and an appreciable unused dead space remains inside the unit housing. Thus, the overall size and noise of the unit cannot be decreased by such methods.
Other prior art condensers used in refrigerating units are known as follows.
U.S. Pat. No. 4,190,102 by Gerz shows a condenser installation having first and second heat exchange means, each including parallel flow passages, wherein the output of the first heat exchange means passes to the second heat exchange means. The flows paths in each of the first and second heat exchange means appear to be in parallel rather than in series. Further, steam from a steam conduit is fed to a chamber in the second heat exchange means.
U.S. Pat. No. 6,089,039 by Yamaguchi discloses, in FIGS. 9 and 11 thereof, a refrigerating unit which includes first and second stage condensers which require a crossflow coupling. In the embodiment shown in FIG. 11, the first stage condenser functions as an evaporator during heating, while the second stage condenser functions as a condenser, and thus the first and second condenser stages perform different functions at different times.
U.S. Pat. No. 6,092,377 by Tso discloses a two stage condenser for an air conditioning or refrigeration system. An upper or main heat exchanger coil is cooled by a fan, while a lower condenser coil is cooled by a wind wheel. A partition therebetween defines a laterally directed exhaust port. Again, although two stages are provided, the condenser overall is a single unit and other refrigeration circuit components (i.e., compressor, evaporator, etc.) are not disposed between the condenser stages.
The present invention is characterized by providing a condenser unit that is divided into two parts, one of which is primarily dedicated to the gas phase of a condensing refrigerant medium, and the other of which is dedicated to the liquid phase of the condensed refrigerant medium. To accommodate this object of the invention, the effective pipe diameter in the second condenser is less than in the first, so that the dimension of the second condenser is also smaller than the first, and moreover, the dimensions of each condenser are decreased in comparison with a single large condenser as known in the prior art. The condensers may be disposed at respective ends of a housing base of the refrigerating unit, with other refrigeration circuit components, i.e., the compressor, evaporator, etc., being disposed between the two condenser sections. Thus, the arrangement results in more efficient use of space and a smaller and quieter refrigerating unit overall.
Because the effective pipe diameter in the second condenser is smaller than in the first, the decreased volume of the refrigerant as it condenses into a liquid is compensated for and the flow velocity of the refrigerant in the liquid phase is kept sufficiently and desirably high. Thus, condenser efficiency, as indicated by the overall heat transfer coefficient (k value) is raised, and at the same time, the refrigerating unit can be designed with a smaller overall size.
Further, because the first and second condensers are smaller than a conventional single-unit condenser, in place of one large fan and fan motor, two smaller fans each having its own motor, are used. As a result, the overall noise produced by the refrigerating unit is actually lower.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.